NHTSA will formally announce the probe Thursday, the official said. As of last week, NHTSA said it had collected more than 80 complaints about steering problems in 2009 and 2010 Corollas.

Many of the complaints involve the car drifting at high speeds. Other owners complain of other issues including steering wheel vibrations or exaggerated motions from small steering inputs.

On Thursday morning, a Toyota rep said the company is "aware of [the] complaints ... and are actively investigating the issue. While we have not received official notification from NHTSA, we will certainly cooperate fully with any NHTSA investigation. We're committed to being responsive to our customers."

The automaker's reputation has felt the blow, as sales lag following the massive recalls.

Earlier Wednesday, in Japan, Toyota President Akio Toyoda addressed reporters for the third time in two weeks. He pledged tighter safety controls but said he will not appear before U.S. lawmakers at hearings to be held next week.

The Associated Press reported that at the Japan press conference, Toyota's executive in charge of quality controls said it was still uncertain if a Corolla recall was necessary, but that it was an option the company was considering.

The Los Angeles city attorney is suing four major retailers over claims that they deliberately inflated the original price on some items that misled customers into thinking they were getting a better deal. More